This invention relates to integrated circuits ("ICs"), and more particularly, to a linear, bipolar-type, analog, application-specific integrated circuit ("ASIC") having a continuous column array architecture of complementary bipolar analog device primitives that enhances simple interconnection among and between the primitives and other components.
Control systems in the aircraft industry are used in various aspects, such as gas turbine engine controls, flight controls, advanced avionic data systems and guidance systems. Over time, increased reliability standards and more stringent size and weight limitations have continued to be imposed upon the electronic circuitry that forms the heart of these control systems. Specifically, increases in the number of control loop parameters, redundancy control, flight control navigation functions, and fire control are just some of the common features now being implemented by electronic circuitry within aircraft flight controls.
These increased functions, together with the reduced size requirements, have resulted in greater efforts to reduce the number of electronic components and interconnections. One avenue explored has been the merging of discrete analog circuit functions into ASICs. Traditionally, ASICs have been reserved for strictly digital logic implementations. It has been recognized that the size of an aircraft control system is largely determined by the amount of analog circuitry and not the digital circuitry. As such, a continuous development effort in linear, bipolar-type analog ASICs is required.
It has been known in the past to create full-custom, linear analog ICs. Such full-custom IC design requires hand crafting of the IC design at the silicon transistor level, requiring an all-level mask definition. One problem with the full-custom approach is that it becomes unfeasible when the ASIC component development occurs in conjunction with the new products in which it is used.
In view of these and other problems inherent with the full-custom approach, it is known to use a semi-custom approach to developing linear ICs. Such an approach utilizes an array architecture of analog circuits, such as current mirrors, op-amps, comparators and current sources, fabricated from a large number of interconnected components, such as bipolar PNP and NPN transistors, resistors, capacitors and diodes. The components are electrically connected into the resulting desired circuits by one or more application-specific, customer-defined metal layers.
However, the interconnection of discrete components in a semi-custom linear, array-type ASIC has historically been a relatively long, time-consuming, manual process. This is in contrast to digital ASICs, where component interconnection is usually done by automatic means; that is, through use of computer-aided design ("CAD") systems. Linear ASIC interconnection difficulty in prior-art designs can be attributed to the substrate placement, content and limited number of transistors available in prior art ASIC architectures. Typically, current state-of-the-art linear ASICs use a predetermined number of device primitives, such as bipolar NPN and PNP transistors, together with diodes, capacitors and resistors in a replicated tile structure that is personalized by metal connections for the end circuit application. Usually, a library of pre-defined cells comprising the various components are used to create functional circuit elements, such as voltage references, op-amps and comparators.
However, this type of replicated tile structure limits standard cell size and wastes tile component residue. That is, not all of the transistors and/or the other components on the substrate are utilized when building the functional circuit elements. This problem is inherent in the design of the replicated tile structure. Another inherent problem is that certain circuits have limited physical locations on the semiconductor substrate. Also, tile component orientation and interconnect channel width pose routing difficulty with standard circuit topologies.
Accordingly, it is a primary object of the present invention to provide a linear, bipolar-type ASIC having an array architecture with one or more continuous columns of array cells comprised of device primitives (i.e., transistors) and other components.
It is a general object of the present invention to provide a linear, bipolar-type ASIC having a transistor level array that allows for full personalization of the primitives and other components, thereby allowing considerable design flexibility.
It is a further object of the present invention to provide a linear, bipolar-type ASIC having a continuous column architecture that allows for placement of laser-trimmable, thin film resistors and power/ground planes in and between, or adjacent to, any two columns and between columns and the bond pads disposed around the outer periphery of the ASIC substrate.
It is yet another object of the present invention to provide a linear, bipolar-type ASIC having an array architecture of analog, bipolar complementary NPN and PNP transistors having high-accuracy, high-frequency and high-temperature operation.
It is still another object of the present invention to provide a linear, bipolar-type ASIC with a continuous column architecture fabricated using an advanced, complementary bipolar linear, bonded-wafer SOI process technology.
It is a further object of the present invention to provide a linear, bipolar-type ASIC with an array architecture of transistor primitives that can be personalized for individual, desired circuits through use of automatic means, such as CAD tools.
Another object of the present invention is to provide a linear, bipolar-type ASIC having a continuous column array architecture that allows wide latitude in the arrangement, distribution, spacing and indexed placement of circuits formed from the various components fabricated on the semiconductor substrate.
Still another object of the invention is to provide a linear, bipolar-type ASIC with a continuous column array architecture that has a relative increase in component density over prior-art designs.
The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.